Why are many anthracite seams mined underground?

Anthracite seams are generally mined using underground methods primarily because of their geological characteristics. Unlike other forms of coal, anthracite typically occurs in geologically deformed areas, such as intensely folded sedimentary rocks.1

The choice between surface and underground mining is dictated by technological factors, including the thickness, steepness, and depth of the coal seam, as well as the nature of the overlying strata. Because anthracite deposits are often found in complex, folded geological structures rather than flat, shallow basins, surface mining is frequently impractical or uneconomical. Consequently, underground mining is the preferred method for extracting this highly metamorphosed fuel.21